1. Field of the Invention
The present invention relates generally to guiding devices, and in a more particular sense has reference to a device of this general nature that is intended specifically to be used in cutting fiber glass duct board. Even more particularly, the invention falls in that category of measuring and guiding devices wherein the guiding device has no moving parts, may be guided along the length of a fiber glass duct board panel in overlying relation thereto, and itself provides a straight guiding edge for a conventional cutting tool.
2. Description of the Prior Art
In recent years, heating and air conditioning ducts have come to be made in sections, each of which is of rectangular cross section and is formed from a single sheet of fiber glass panel material. The fiber glass panel from which the duct section is made typically is formed with a base of bendable aluminum sheet material, to which a relatively thick layer of fiber glass insulation is adhered. This material is provided, customarily, in the form of flat sheets.
In order to form a duct section from a panel of this type, the panel is laid out flat on the floor or on a table, and measurements are carefully made along the length of the panel, for the purpose of locating the centers of V grooves that are to be formed in the panel by means of a cutting tool. The cutting tool is usually of the hand-held type.
The V grooves extend to a depth such that the apices thereof terminate substantially at the base lamination. The base layer of the panel is itself not cut. Accordingly, after three V grooves have been formed at the proper locations, the panel is bent into a rectangular cross sectional shape. Opposite end edges of the panel are typically formed with shiplap grooves, that interfit when the panel is bent into its final form to provide the desired rectangular duct section. The shiplapped edges are then secured together, by taping the same over the full length of the duct section.
In the formation of ducts of this type, great care has been required heretofore, in making the required measurements on the flat panel, and in thereafter guiding the tool along lines marked upon the panel at the locations where the V grooves are to be cut.
The measuring of the panel must be carried out with great precision. If a measurement between adjacent V grooves is off even by a fraction of an inch, the resulting duct will not be perfectly rectangular, and will be incapable of being secured in abutting relation to adjacent duct sections.
It follows that it is equally a precision task to guide the cutting tool along the markings applied to the panel during the measuring phase of the duct manufacturing operation. For, even if the measurement is absolutely correct, the failure to guide the cutting tool with absolute precision along the marking again results in a misshapen duct section that would have to be discarded with an attendant, non recoverable expense in lost material and labor.
Recognizing these basic and important requirements in the formation of ducts of the character described, the industry has offered various solutions. For example, expensive and relatively complicated apparatus has been devised, which apart from the basic cost thereof, requires considerable set-up time and the adjustment of a large number of components during the measuring and cutting operation. Even so, apparatus of this type typically requires that the ductwork be manufactured in a shop setting, often great distances from the building job where the ductwork is to be ultimately installed. This involves, as will be readily understood, the transportation of completed ductwork by truck or other vehicle to the building site, at great expense and with considerable added possibility of damage being done to the ductwork before it can be put in place.
Other systems for the formation of ducts of this type have also been devised, which in the final analysis open up an overly great number of possibilities for human error. In these circumstances, in order to reduce the possibility of human error, it becomes necessary to utilize highly skilled labor, a step which obviously builds up the overall cost of the ductwork.
To overcome these deficiencies in the prior art devices used in forming fiber glass duct sections, it is proposed in accordance with the present invention to provide a very simple, lightweight, compact tool having no moving parts, and adapted to be carried to any job site to permit formation of ducts directly at the site, ready for installation without need of transport to another location.
A further important aim of the present invention is to so form the tool as to permit it to be used by unskilled, relatively low cost labor with relatively little instruction.
It is further proposed, in overcoming the deficiencies of the prior art apparatus, that the tool comprising the present invention be so designed as to reduce to a minimum the possibility of human error, even though relatively inexperienced labor, having only a short period of instruction, is used.
Another object of importance is to reduce to a minimum the total amount of time within which a flat panel is transformed into a completed duct section by eliminating the steps of pre-measurement and marking of the panel, and/or eliminating the necessity of pre-setting various components of a cutting machine or other apparatus before the actual cutting is performed.